Conversion of hydrocarbons



Patented May 10, 1938 PATENT OFFICE CONVERSION F HYDROCARBONS Paul L. Cramer, Highland Park, Mich, assignor, by mesne assignments, to General'Motors Corporation, Detroit, Mich., a corporation of Delaware No Drawing.

Application January 4, 1934,

Serial No. 705,237

8 Claims.

This invention relates to the conversion of hydrocarbons, particularly thoseof the unsaturated aliphatic type into hydrocarbons of higher boiling points. It is well-known that considerable quantities of unsaturated hydrocarbons, especially those of the olefin series, are commercially available as raw materials and it is the primary object of the invention to provide a method whereby such materials may be converted into 10 more valuable products such as lubricating oils or fuels of high quality.

I have found that hydrocarbons of lower boiling points may be polymerized or otherwise converted into hydrocarbons of higher boiling points by subjecting them to suitable temperatures and pressures in the presence of alkyl or aryl radicals. The hydrocarbon radicals, preferably alkyl radicals such as methyl, ethyl, butyl and the like, are preferably introduced into the reaction chamber by direct decomposition of metal comcompounds.

The activity of the reaction or the yield of converted products is greatly affected by the phase of the reacting materials and I find it highly desirable to maintain the materials in the liquid phase. This may be accomplished by the presence of a solvent, which may, itself, be relatively inert, and which is liquid at the temperatures and pressures employed. This may, however, be supplied at least in part by theproducts of conversion. Hydrocarbons which will remain liquid at the temperatures and pressures involved are suitable solvents. Benzene and naphthalene may be usedas inert solvents.

The temperature employed may be relatively low as compared with the temperatures required for usual cracking processes preferably not above approximately 300 C. The principal consideration is that the temperature be suflicient to cause decomposition of the metal alkyl employed as a source of the alkyl radicals. For example, a temperature of 180 C., is suificient to cause decomposition of tetraethyl lead and temperatures in general not exceeding approximately 275 (2,..have been found quite suflicient in carrying 'o1 1t the process with ethylene as the raw material and tetraethyl lead as the source of the activating radicals. Relatively low temperatures are especially desirable because cracking with the resultant formation of carbon and other undesirable products may thereby be avoided.

The pressure to be employed is largely depend ent upon the materials used, and, in a static or batch procedure, will vary with the progress of pounds of the radicals such as lead or mercury the reaction. The principal consideration is to maintain a high concentration of the reacting hydrocarbons in relation to the activating radicals. The pressure desirable will be related to the vapor pressure of the materials and the temperature should be maintained below the critical temperature of the solvent.

The reactions which take place. are apparently quite complex and go beyond a mere combination of the radicals derived from the metal compound with the hydrocarbon used as a raw material, since a relatively small amount of the metal compound brings about the conversion of a relatively great quantity of .the hydrocarbon. It appears that the action of the radicals is in a sense catalytic in that they are to a large extent regenerated in the progress of the reaction and again become available to activate further chain formations in the hydrocarbon molecules. A certain proportion of the radicals do, however, become combined or become inactive in the product so that a continuous process will require the constant addition of smallquantities of the metal compound. 7

The choice of the metal compound depends upon several factors, one being commercial availability. So far as the conditions of the process are concerned, there are two principal considerations, one being the temperature at which the compound decomposes to yield the radicals and the other being the character of the residual substance. This residue should preferably be inert and readily separable from the desirable end products. For this reason the lead and mercury aikyls are especially recommended, although other metal alkyl and aryl compounds decomposable at relatively low temperatures have been found operable.

The time during which the reaction may be continued will ailect the product, a longer time resulting in a higher proportion of high boiling constituents.

The endproduct will depend also upon the raw material since higher boiling olefins, such as heptene, will be converted into higher boiling products than will the lower boiling olefins, such as ethylene, other conditions being equaL. One marked advantage in the process is that the product is remarkably free from undesirable constituents, being according to my experience, a colorless oil capable of being fractionated to yield engine fuels of high anti-knock properties and lubricating oils of excellent quality.

A similar reaction occurs with some of the saturated paraffin and hydrogenated aromatic hydrocarbons. For example, I have obtained over 30% of'conversion in the treatment of ndecane, and as high as in the treatment of tetralin.

As a specific example of a demonstration of the process, 0.0005 mol. of tetraethyl lead was added to 0.684 mol. of ethylene in 50 c. c. of benzene in a reaction bomb. The bomb was subjected to a temperature not exceeding approximately 275 C., for about four hours during which the pressure reached a maximum of 1900 lbs. per square inch. About of the ethylene was converted to a colorless oil.

I claim:

1. The process of producing higher boiling hy-.

drocarbons from hydrocarbons of lower boiling points comprising heating said lower boiling hydrocarbons in the liquid phase in the presence of a hydrocarbon compound of a metal of the class consisting of lead and mercury, said compound being one which upon heating decomposes to yield ahydrocarbon radical, said radicals combining with the said lower boiling hydrocarbon and promoting polymerization and conversion thereof to yield higher boiling hydrocarbons. the temperature ofthe reacting mixture being sufflcient to effect liberation of hydrocarbon radicals from said compound and below that at which material cracking effects will occur.

2. Process as in claim 1, the upper limit of temperature being approximately 300 C. and the said compound being a metal alkyl.

3. Process as in claim 1, the lower boiling hydrocarbons being oleflnic.

4. The process of producing higher boiling oils from hydrocarbons of lower boiling points comprising heating said lower boiling hydrocarbons in the liquid phase to temperatures not substantially in excess of 300 C. in the presence of a catalyst, said catalyst being an alkyl compound oi a metal from the group consisting of lead and mercury and acting to promote polymerization and conversion of said lower boiling hydrocarbons to yield hydrocarbons of higher boiling points.

5. Process as set forth in claim-4, the lower boiling hydrocarbons being olefinic.

6. The process of producing higher boiling oils comprising heating a liquid mixture containing ethylene and a metal alkyl to a temperature sufllcient to decompose the metal alkyl thereby freeing alkyl radicals which combine with ethylene and promote its conversion to higher boiling hydrocarbons, said metal being one of the class consisting of lead and mercury.

7. The process of producing higher boiling oils from ethylene comprising heating a liquid mixture containing ethylene and tetraethyl lead to a temperature sufiicient to decompose the tetraethyl lead to free hydrocarbon radicals from the tetraethyl lead, said radicals combining with the ethylene and promoting ,conversion thereof to higher boiling hydrocarbons.

' 8. The process of producing higher boiling oils from olefinic hydrocarbons of lower boiling points comprising preparing a mixture of the said hydrocarbons and a solvent therefor, adding to said mixture a compound of a hydrocarbon radical and a metal of the class consisting of lead and mercury, heating the mixture to a temperature sufficient to decompose the metal compound to yield the hydrocarbon radical and maintaining the temperature below the critical temperature of the solvent, the freed radicals combining with the said olefins and promoting polymerization and conversion thereof to yield higher boiling hydrocarbons suitable for fuels and lubricating oils.

PAUL L. CRAMER. 

